/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iceberg.avro;

import java.io.IOException;
import java.util.function.Supplier;
import org.apache.avro.Schema;
import org.apache.avro.io.DatumReader;
import org.apache.avro.io.Decoder;
import org.apache.iceberg.mapping.NameMapping;

/**
 * A delegating DatumReader that applies a name mapping to a file schema to enable reading Avro
 * files that were written without field IDs.
 *
 * @param <D> Java class of datums produced by this reader
 */
public class NameMappingDatumReader<D> implements DatumReader<D>, SupportsRowPosition {
  private final NameMapping nameMapping;
  private final DatumReader<D> wrapped;

  public NameMappingDatumReader(NameMapping nameMapping, DatumReader<D> wrapped) {
    this.nameMapping = nameMapping;
    this.wrapped = wrapped;
  }

  @Override
  public void setSchema(Schema newFileSchema) {
    Schema fileSchema;
    if (AvroSchemaUtil.hasIds(newFileSchema)) {
      fileSchema = newFileSchema;
    } else {
      fileSchema = AvroSchemaUtil.applyNameMapping(newFileSchema, nameMapping);
    }

    wrapped.setSchema(fileSchema);
  }

  @Override
  public D read(D reuse, Decoder in) throws IOException {
    return wrapped.read(reuse, in);
  }

  @Override
  public void setRowPositionSupplier(Supplier<Long> posSupplier) {
    if (wrapped instanceof SupportsRowPosition) {
      ((SupportsRowPosition) wrapped).setRowPositionSupplier(posSupplier);
    }
  }
}
